<?php

/*
 * Project:     MagpieRSS: a simple RSS integration tool
 * File:        rss_cache.inc, a simple, rolling(no GC), cache 
 *              for RSS objects, keyed on URL.
 * Author:      Kellan Elliott-McCrea <kellan@protest.net>
 * Version:     0.51
 * License:     GPL
 *
 * The lastest version of MagpieRSS can be obtained from:
 * http://magpierss.sourceforge.net
 *
 * For questions, help, comments, discussion, etc., please join the
 * Magpie mailing list:
 * http://lists.sourceforge.net/lists/listinfo/magpierss-general
 *
 */

class RSSCache
{

    var $BASE_CACHE = './cache';    // where the cache files are stored
    var $MAX_AGE = 3600;         // when are files stale, default one hour
    var $ERROR = "";           // accumulate error messages

    function RSSCache($base='', $age='')
    {
        if ($base)
        {
            $this->BASE_CACHE = $base;
        }
        if ($age)
        {
            $this->MAX_AGE = $age;
        }

        // attempt to make the cache directory
        if (!file_exists($this->BASE_CACHE))
        {
            $status = @mkdir($this->BASE_CACHE, 0755);

            // if make failed
            if (!$status)
            {
                $this->error(
                        "Cache couldn't make dir '" . $this->BASE_CACHE . "'."
                );
            }
        }
    }

    /* =======================================================================*\
      Function:   set
      Purpose:    add an item to the cache, keyed on url
      Input:      url from wich the rss file was fetched
      Output:     true on sucess
      \*======================================================================= */

    function set($url, $rss)
    {
        $this->ERROR = "";
        $cache_file = $this->file_name($url);
        $fp = @fopen($cache_file, 'w');

        if (!$fp)
        {
            $this->error(
                    "Cache unable to open file for writing: $cache_file"
            );
            return 0;
        }


        $data = $this->serialize($rss);
        fwrite($fp, $data);
        fclose($fp);

        return $cache_file;
    }

    /* =======================================================================*\
      Function:   get
      Purpose:    fetch an item from the cache
      Input:      url from wich the rss file was fetched
      Output:     cached object on HIT, false on MISS
      \*======================================================================= */

    function get($url)
    {
        $this->ERROR = "";
        $cache_file = $this->file_name($url);

        if (!file_exists($cache_file))
        {
            $this->debug(
                    "Cache doesn't contain: $url (cache file: $cache_file)"
            );
            return 0;
        }

        $fp = @fopen($cache_file, 'r');
        if (!$fp)
        {
            $this->error(
                    "Failed to open cache file for reading: $cache_file"
            );
            return 0;
        }

        if ($filesize = filesize($cache_file))
        {
            $data = fread($fp, filesize($cache_file));
            $rss = $this->unserialize($data);

            return $rss;
        }

        return 0;
    }

    /* =======================================================================*\
      Function:   check_cache
      Purpose:    check a url for membership in the cache
      and whether the object is older then MAX_AGE (ie. STALE)
      Input:      url from wich the rss file was fetched
      Output:     cached object on HIT, false on MISS
      \*======================================================================= */

    function check_cache($url)
    {
        $this->ERROR = "";
        $filename = $this->file_name($url);

        if (file_exists($filename))
        {
            // find how long ago the file was added to the cache
            // and whether that is longer then MAX_AGE
            $mtime = filemtime($filename);
            $age = time() - $mtime;
            if ($this->MAX_AGE > $age)
            {
                // object exists and is current
                return 'HIT';
            }
            else
            {
                // object exists but is old
                return 'STALE';
            }
        }
        else
        {
            // object does not exist
            return 'MISS';
        }
    }

    function cache_age($cache_key)
    {
        $filename = $this->file_name($url);
        if (file_exists($filename))
        {
            $mtime = filemtime($filename);
            $age = time() - $mtime;
            return $age;
        }
        else
        {
            return -1;
        }
    }

    /* =======================================================================*\
      Function:   serialize
      \*======================================================================= */

    function serialize($rss)
    {
        return serialize($rss);
    }

    /* =======================================================================*\
      Function:   unserialize
      \*======================================================================= */

    function unserialize($data)
    {
        return unserialize($data);
    }

    /* =======================================================================*\
      Function:   file_name
      Purpose:    map url to location in cache
      Input:      url from wich the rss file was fetched
      Output:     a file name
      \*======================================================================= */

    function file_name($url)
    {
        $filename = md5($url);
        return join(DIRECTORY_SEPARATOR, array($this->BASE_CACHE, $filename));
    }

    /* =======================================================================*\
      Function:   error
      Purpose:    register error
      \*======================================================================= */

    function error($errormsg, $lvl=E_USER_WARNING)
    {
        // append PHP's error message if track_errors enabled
        if (isset($php_errormsg))
        {
            $errormsg .= " ($php_errormsg)";
        }
        $this->ERROR = $errormsg;
        if (MAGPIE_DEBUG)
        {
            trigger_error($errormsg, $lvl);
        }
        else
        {
            error_log($errormsg, 0);
        }
    }

    function debug($debugmsg, $lvl=E_USER_NOTICE)
    {
        if (MAGPIE_DEBUG)
        {
            $this->error("MagpieRSS [debug] $debugmsg", $lvl);
        }
    }

}

?>
